1. Field of the Invention
This invention relates generally to a flexible disc recording and/or reproducing apparatus, and more particularly is directed to an arrangement for accurately positioning a flexible rotated disc while an information signal, such as, a video or still picture signal, is being recorded or reproduced on a surface of the disc by means of a magnetic head or heads.
2. Description of the Prior Art
Apparatus has been provided in which a video or other information signal is recorded and/or reproduced by a magnetic head in a substantially circular record track formed on a flexible magnetic disc while the latter is rotated at a relatively high speed, for example, a speed of 1800 or 3600 RPM. The flexible magnetic disc used for such recording or reproducing may be extremely thin, for example, it may have a thickness of about 40 .mu.m. Therefore, as shown on FIG. 1A, the flexible magnetic disc C is usually contained in a jacket or cartridge casing A for preventing crumpling, folding or other damage to the relatively fragile disc, particularly when not in use. The jacket or cartridge casing A has central openings in its opposite walls at which the center of the disc can be engaged by a drive for effecting the high speed rotation of the disc while contained in the jacket or cartridge which is further provided with a window B through which the magnet head may contact the disc surface for recording or reproducing the information signal thereon. In existing flexible disc recording and/or reproducing apparatus, the disc has a relatively large diameter, for example, of the order of 30 .mu.m. Therefore, when the flexible disc C is rotated at a relatively high speed within the jacket or cartridge casing A as mentioned above, the resulting centrifugal forces are relatively large to urge the flexible disc to maintain a flat configuration in a plane normal to the rotational axis. Further, the high speed rotation of the flexible disc causes the generation of air flows or films moving radially outward from the center of the rotated disc C toward the periphery between the disc surfaces and the adjacent walls A.sub.1 and A.sub.2 of the jacket or cartridge casing A, as indicated by the arrows on FIG. 1B. As a result of the foregoing, a magnetic head may be pressed against the surface of the rotated flexible disc C without substantial movement of the latter away from the head due to the stretching of the disc. Therefore, in the case of a flexible disc of relatively large diameter, the attainment of stable and reliable contact of the magnetic head with the disc surface does not present a serious problem.
However, in order to facilitate the handling of a jacket or cartridge casing containing a flexible magnetic disc, for example, to permit the convenient storage or mailing thereof, it is desirable to reduce the diameter of the flexible disc. When the diameter of the disc is reduced sufficiently for the foregoing purposes, it is difficult to attain adequate air flows and centrifugal forces acting on the flexible rotated disc for ensuring the reliable and stable contact of the magnetic head with the disc surface.